// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ui/views/corewm/cursor_height_provider_win.h"

#include <algorithm>
#include <map>
#include <stddef.h>
#include <stdint.h>
#include <windows.h>

#include "base/memory/scoped_ptr.h"
#include "base/win/scoped_hdc.h"

namespace {
using PixelData = scoped_ptr<uint32_t[]>;
using HeightStorage = std::map<HCURSOR, int>;

const uint32_t kBitsPeruint32 = sizeof(uint32_t) * 8;
// All bits are 1 for transparent portion of monochromatic mask.
const uint32_t kTransparentMask = 0xffffffff;
// This is height of default pointer arrow in Windows 7.
const int kDefaultHeight = 20;
// Masks are monochromatic.
const size_t kNumberOfColors = 2;
const size_t KHeaderAndPalette = sizeof(BITMAPINFOHEADER) + kNumberOfColors * sizeof(RGBQUAD);

HeightStorage* cached_heights = nullptr;

// Extracts the pixel data of provided bitmap
PixelData GetBitmapData(HBITMAP handle, const BITMAPINFO& info, HDC hdc)
{
    PixelData data;
    // Masks are monochromatic.
    DCHECK_EQ(info.bmiHeader.biBitCount, 1);
    if (info.bmiHeader.biBitCount != 1)
        return data.Pass();

    // When getting pixel data palette is appended to memory pointed by
    // BITMAPINFO passed so allocate additional memory to store additional data.
    scoped_ptr<char[]> header(new char[KHeaderAndPalette]);
    memcpy(header.get(), &(info.bmiHeader), sizeof(info.bmiHeader));

    data.reset(new uint32_t[info.bmiHeader.biSizeImage / sizeof(uint32_t)]);

    int result = GetDIBits(hdc,
        handle,
        0,
        info.bmiHeader.biHeight,
        data.get(),
        reinterpret_cast<BITMAPINFO*>(header.get()),
        DIB_RGB_COLORS);

    if (result == 0)
        data.reset();

    return data.Pass();
}

// Checks if the specifed row is transparent in provided bitmap.
bool IsRowTransparent(const PixelData& data,
    const uint32_t row_size,
    const uint32_t last_byte_mask,
    const uint32_t y)
{
    // Set the padding bits to 1 to make mask matching easier.
    *(data.get() + (y + 1) * row_size - 1) |= last_byte_mask;
    for (uint32_t i = y * row_size; i < (y + 1) * row_size; ++i) {
        if (*(data.get() + i) != kTransparentMask)
            return false;
    }
    return true;
}

// Gets the vertical offset between specified cursor's hotpoint and it's bottom.
//
// Gets the cursor image data and extract cursor's visible height.
// Based on that get's what should be the vertical offset between cursor's
// hot point and the tooltip.
int CalculateCursorHeight(HCURSOR cursor_handle)
{
    base::win::ScopedGetDC hdc(NULL);

    ICONINFO icon = { 0 };
    GetIconInfo(cursor_handle, &icon);

    BITMAPINFO bitmap_info = {};
    bitmap_info.bmiHeader.biSize = sizeof(bitmap_info.bmiHeader);
    if (GetDIBits(hdc, icon.hbmMask, 0, 0, NULL, &bitmap_info, DIB_RGB_COLORS) == 0)
        return kDefaultHeight;

    // Rows are padded to full DWORDs. OR with this mask will set them to 1
    // to simplify matching with |transparent_mask|.
    uint32_t last_byte_mask = 0xFFFFFFFF;
    const unsigned char bits_to_shift = sizeof(last_byte_mask) * 8 - (bitmap_info.bmiHeader.biWidth % kBitsPeruint32);
    if (bits_to_shift != kBitsPeruint32)
        last_byte_mask = (last_byte_mask << bits_to_shift);
    else
        last_byte_mask = 0;

    const uint32_t row_size = (bitmap_info.bmiHeader.biWidth + kBitsPeruint32 - 1) / kBitsPeruint32;
    PixelData data(GetBitmapData(icon.hbmMask, bitmap_info, hdc));
    if (data == NULL)
        return kDefaultHeight;

    // There are 2 types of cursors: Ones that cover the area underneath
    // completely (i.e. hand cursor) and ones that partially cover
    // and partially blend with background (i. e. I-beam cursor).
    // These will have either 1 square mask or 2 masks stacked on top
    // of each other (xor mask and and mask).
    const bool has_xor_mask = bitmap_info.bmiHeader.biHeight == 2 * bitmap_info.bmiHeader.biWidth;
    const int cursor_height = has_xor_mask ? static_cast<int>(bitmap_info.bmiHeader.biHeight / 2)
                                           : static_cast<int>(bitmap_info.bmiHeader.biHeight);
    int xor_offset;
    if (has_xor_mask) {
        for (xor_offset = 0; xor_offset < cursor_height; ++xor_offset) {
            const uint32_t row_start = row_size * xor_offset;
            const uint32_t row_boundary = row_start + row_size;
            for (uint32_t i = row_start; i < row_boundary; ++i)
                data.get()[i] = ~(data.get()[i]);
            if (!IsRowTransparent(data, row_size, last_byte_mask, xor_offset)) {
                break;
            }
        }
    } else {
        xor_offset = cursor_height;
    }

    int and_offset;

    for (and_offset = has_xor_mask ? cursor_height : 0;
         and_offset < bitmap_info.bmiHeader.biHeight; ++and_offset) {
        if (!IsRowTransparent(data, row_size, last_byte_mask, and_offset)) {
            break;
        }
    }
    if (has_xor_mask) {
        and_offset -= cursor_height;
    }
    const int offset = std::min(xor_offset, and_offset);

    DeleteObject(icon.hbmColor);
    DeleteObject(icon.hbmMask);

    return cursor_height - offset - icon.yHotspot + 1;
}

} // namespace

namespace views {
namespace corewm {

    int GetCurrentCursorVisibleHeight()
    {
        CURSORINFO cursor = { 0 };
        cursor.cbSize = sizeof(cursor);
        GetCursorInfo(&cursor);

        if (cached_heights == NULL)
            cached_heights = new HeightStorage;

        HeightStorage::const_iterator cached_height = cached_heights->find(cursor.hCursor);
        if (cached_height != cached_heights->end())
            return cached_height->second;

        const int height = CalculateCursorHeight(cursor.hCursor);
        (*cached_heights)[cursor.hCursor] = height;

        return height;
    }

} // namespace corewm
} // namespace views
